1. Field of the Invention
The present invention relates to a method for processing a polysilazane film disposed on a target substrate, such as a silicon wafer, and particularly to a method preferably applied to a semiconductor process. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or a glass substrate used for an FPD (Flat Panel Display), e.g., an LCD (Liquid Crystal Display), by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
2. Description of the Related Art
In general, a silicon oxide film (SiO2 film) is used as an insulating film, such as the device isolation film of an STI (Shallow Trench Isolation) structure or the inter-level insulating film of a PMD (Pre-Metal Dielectric) structure, for semiconductor devices. As a method for forming a silicon oxide film of this kind, a process for forming an insulating film by CVD (Chemical Vapor Deposition), such as a BPSG (Boron Phospho-Silicate Glass) method or ozone TEOS (TetraEthyl Ortho-Silicate) method, is used, in general.
In recent years, semiconductor devices have become smaller with an increase in integration degree (for example, semiconductor devices of a generation having a line width of less than 0.13 μm), thereby increasing the aspect ratio of trenches for STI and recesses, e.g., gaps between members thereof. Where a method, such as the BPSG method or ozone TEOS method described above, is used to form an SiO2 film to fill a recess having a high aspect ratio, a problem arises such that the SiO2 film is very poor in filling the recess (step coverage).
In order to improve the step coverage for a recess having a high aspect ratio, researches have been conducted to use a polysilazane (—(SiR1-NR2)n-: R1 and R2 represent alkyl groups) film as a device isolation film or inter-level insulating film. Where a polysilazane film is formed, a polysilazane coating solution is applied onto a target substrate, and is then subjected to a heat process, so that it is baked into an insulating film containing silicon and oxygen (typically, a silicon oxide film (SiO2 film)). Silicon oxide films of this coating type excel in step coverage, and have an advantage in that they can become dense by a heat process performed within a water vapor atmosphere, so that they do not have voids or seams formed therein.